In past, apparatus of detecting physiological function is often of huge volume so as to be put in a health center, and people can't help but go to the health center where it is put for detecting health condition. At that time, it is not easy for people to execute detection at any time they want. However, along with progress of medical and semiconductor technologies, present detection apparatus has been of smaller volume and further able to be mounted onto body, which is called wearable device with real time detection.
Present wearable device may detect user's various physiological data, such as body temperature, breathe, heartbeat, pedestrian time or distance, and so on. Among these physiological data, heartbeat may reflect important information about personal health. Heart rhythm represents signal of heartbeat interval in a fixed period and reflects heart condition. There are two detection approaches for heart rhythm: optical transmittance measurement and electric signal measurement. The optical transmittance measurement is also called photoplethysmography, which illuminates skin and measures changes in light absorption or reflection for acquisition of heartbeat condition. The principle of the optical transmittance measurement is based on constant light absorption by skin or muscle tissue at specific zones of human body, but amount of light absorption can be influenced by blood volume within skin. When heart pumps, the blood volume within skin can have pulsation change. When heart contracts, peripheral blood volume is the biggest, so that light absorption is the most, too. Accordingly, when there is a little change in reflected light detected by light sensor, it is supposed to have one heartbeat. Because there is specific wavelength light absorption for blood, huge amount of light of the specific wavelength will be absorbed when heart pumps every time, and heartbeat may be determined by measuring reflected or absorbed light signal. However, too much power consumption and its subjected to interference by ambient light outside are disadvantages for optical transmittance measurement. On the other hands, electric signal measurement has a principle similar to electrocardiogram method, which direct measures electric signals generated from heart beats by a sensor to judge user's heart rhythm condition. There are drawbacks for such a method, such as complicated circuit and the sensor needed to be tightly attached onto skin and fixed, so it is not suitable for wearable device like wrist ring or watch.
Present wearable devices often utilize optical transmittance measurement to monitor user's heart beats because of its light weight and compact volume to reduce user's loading when wearing it. Thus, how to analyze the signal detected by optical transmittance measurement for wearable device will influence analysis accuracy for physiological signal and become a key issue. On the other hand, complicated analysis method not only utilizes huge circuit for processing but also causes much power consumption to reduce power continue voyage ability in standby. Thus, how to make balances among detection accuracy, low consumption, and light and compact volume is an important issue for designing wearable device.
In order to resolve the drawbacks aforementioned, there are technologies to look for wearable device cooperated with portable device. With wireless transmission, the wearable device transmits detected signal to portable device for performing analysis and display of the detected signal. Though circuit volume and power consumption of wearable device may not be influenced even with more complex analysis and calculation, however, such cooperation approach results in wearable device unable to use independently, and user needs to pick up portable device for checking physiological condition. Both convenience and intuitiveness in use will be destroyed. Thus, it is not a perfect solution. Besides, over power consumption is still an issue because wearable device still transmits huge volume signals to exterior device by wireless transmission method.
Accordingly, subject to low power consumption and rapid calculation, it is an important issue of the present invention to have a design capable of rapidly detecting signal and analyzing detected signal to provide user precise and accurate physiological data such as heat beat or rhythm.